linux-kernel - Re: [PATCH] kthread: always create the kernel threads with normal priority

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Message-ID: <20080107141014.3815fcca@brian.englab.brq.redhat.com>
Date:	Mon, 7 Jan 2008 14:10:14 +0100
From:	Michal Schmidt <mschmidt@...hat.com>
To:	"Remy Bohmer" <linux@...mer.net>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Jon Masters" <jcm@...hat.com>,
	"Satoru Takeuchi" <takeuchi_satoru@...fujitsu.com>,
	"Steven Rostedt" <rostedt@...dmis.org>
Subject: Re: [PATCH] kthread: always create the kernel threads with normal
 priority

On Mon, 7 Jan 2008 12:22:51 +0100
"Remy Bohmer" <linux@...mer.net> wrote:

> Hello Michal and Andrew,
> 
> > Let's not make the decision for the user. Just allow the
> > administrator to change kthreadd's priority safely if he chooses to
> > do it. Ensure that the kernel threads are created with the usual
> > nice level even if kthreadd's priority is changed from the default.
> 
> Last year, I posted a patchset (that was meant for Preempt-RT at that
> time) to be able to prioritise the interrupt-handler-threads (which
> are kthreads) and softirq-threads from the kernel commandline. See
> http://lkml.org/lkml/2007/12/19/208
> 
> Maybe we can find a way to use a similar mechanism as I used in my
> patchset for the priorities of the remaining kthreads.
> I do not like the way of forcing userland to change the priorities,
> because that would require a userland with the chrt tool installed,
> and that is not that practical for embedded systems (in which there
> could be cases that there is no userland at all, or the init-process
> is the whole embedded application). In that case an option to do it on
> the kernel commandline is more practical.
> 
> I propose this kernel cmd-line option:
> kthread_pmap=somethread:50,otherthread:12,34

I see. kthreadd would look up the priority for itself and
kthread_create would consult the map for all other kernel threads.
That should work.
Your sirq_pmap would not be needed anymore, as kthread_pmap could be
used for softirq threads too, right?

Michal
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